The trick is managing those worker accounts -- I've NEVER heard anyone describe a legitimate system for working with 10,000 accounts and here's why:
for your account to work they need to retweet/follow, etc. to do this you have to log into twitter with them. Now you have an IP address problem. Most people say you can effectively and safely control 5 accounts from one IP but - for the sake of our thought experiment - lets say we're able to use 50 accounts per IP.
For these 10,000 accounts I would need 200 IPs (we have to assume private proxies, not public as I need to be the only one using twitter with them). 200 private proxies is going to run you not less than $200/month.
Not a very cost effect twitter management strategy. Please if I am wrong or someone knows an obvious way around the math I'm doing, I'd love to know it.